In regard to vehicle window glasses, for the solder (solder alloy) that connects between a power supply terminal and a wiring formed from a silver paste on a glass plate serving as a base, solder containing lead has been conventionally used. However, in recent years, the influence of lead on the environment and the like have been raised as a matter, and thus transition to the use of lead-free solder is underway (see Patent Document 1).
Lead-free solder has higher Young's modulus and high rigidity compared to leaded solder containing lead. Therefore, when a mechanical stress or a stress caused by the difference in the thermal expansion coefficient is applied, there is a possibility that cracks and the like may be generated in the glass plate, or the solder may be peeled off.
Patent Document 1: PCT International Publication No. WO2012/096373